Embodiments of the present disclosure relate to electrical power systems, and more particularly, to hold-up capacitor charging using a fly-back power supply.
Various electronic products make use of a hold-up capacitor to store energy during normal power supply operating conditions. The stored energy is utilized to power up a system for certain duration of time, called the hold-up time, even after the power supply is turned off, either due to a failure condition or a dip in voltage due to overload, etc. During the hold-up time, critical parameter information regarding the status of an electronic unit can be communicated to a next higher level component in a system before the electronic unit shuts down. The hold-up time is proportional to the amount of energy stored in the hold-up capacitor.
To charge the hold-up capacitor, additional circuitry is typically used, such as an additional high-voltage secondary winding on a transformer with a higher voltage than a typical transformer winding along with rectification circuitry, such that the transformer includes at least three windings (e.g., a primary, a secondary, and a higher-voltage secondary). Other approaches include the addition of a boost converter to generate high voltage with an additional power supply circuit. A boost converter typically includes additional storage elements, such as an inductor, switching circuitry, filtering circuitry, and other components. However, these options result in increased size, power consumption, testing burden, and other such issues.